C-30 Repower Advice

Old Skool Neil · Aug 1, 2011

Option 3 is get another opinion.

This mechanic may be right but wouldn't you like to know for sure?

Allan12210 · Aug 1, 2011

Option 3 might be get a new mechanic. Like Neil suggests, a second opinion is absolutely needed. Find someone who does not have a vested interest in performing the job. Understand what could cause low compression...valves, rings etc. Those could require less expensive rebuilds if even necessary. Accurate compression testing on a diesel is tricky. It can be influenced by the gauge, length of hose or how well it was screwed into the cylinder....via glow plug or with a dummy injector. Here's a question for you...Hows it run now?

Do your research before pulling the trigger.

jviss · Aug 2, 2011

Another mechanic

I agree that you should get another opinion. It seems pretty evenly low; I believe the compression should be 450 lb., with 325 the low limit. How did all three cylinders get low at the same time? Could be a loose head, valves (check the compression release), or even just a bad compression gauge or test technique.

Have you tried to start this? How?

jv

jviss · Aug 2, 2011

I wanted to come back to this. My opinion is that repowering a C30 is an extreme measure. It's very expensive and time consuming, and it assumes that the old engine is completely beyond repair. Unless it is your intention to completely restore this boat, and money is no object, I would consider this an absolute worst-case last resort.

I am suspicious of the relatively uniform low compression readings. I'm not saying there's any foul play on the part of the mechanic, I'm just saying it seems odd that all three cylinders would get to 220 to 240 psi together. In my opinion, it's likely that the measurement is incorrect, or, there is some single factor lowering all three cylinder pressures.

I'm not a diesel mechanic (I'm an electrical engineer). But, I have learned a lot about my Kubota diesel in 11 years of owning my C36.

My reasoning is that it doesn't seem that normal wear would wear it out to the point that the compression would be so much lower than what is necessary to start it. If it was an event like overheating, it could affect all three cylinders. I think that is the most likely thing, that the engien was overheated, and burnt the valves.

A maladjusted or partially engaged compression release system could lower your compression. So could a bad head gasket. I would also check for loose, incorrectly torqued injectors, and loose or incorrectly tightened glow plugs.

The next thing I would do is re-torque the head, and then adjust the valves and compression release (which is necessary after a head re-torque). (I've done this). This is pretty easy to do in-place, and fairly quick. It does not require removing the injectors, etc., if I recall correctly, only the valve cover.

If everything above is correct, injectors and glow plugs tight, head bolts tight, valves adjusted correctly, compression release correct, and you are sure the compression is still low, then your next recourse is some diagnostics. The compression leak could only be through the head gasket, piston rings, or valves. Let's assume it's not the head gasket. If you squirt some motor oil into the cylinder and then quickly test the compression, if the compression comes up, then the rings are leaking. If not, it's likely the valves.

I think the valves could have been burnt from overheating. This would be a cylinder head rebuild, much cheaper and quicker than an engine rebuild, and wouldn't require pulling the engine.

If you pull the head you can look at the valves, and at the same time inspect the cylinder walls - for scoring, or glazing, or other damage. Ideally, the walls will have a criss-cross honing pattern still in them (that would be great!); likely, if high hours, they will be glazed, but without obvious damage, the engine would still run, although it would probably smoke some.

Doing anything about cylinder walls and rings will require pulling the engine.

A few questions:

How many total hours?

Has it been sitting a long time without use?

Have you ever seen it run?

Was there an event that stopped it, a failure of some sort? Overheating, etc.?

Any other evidence of overheating?

jv

Stu Jackson · Aug 2, 2011

Good ideas here, too soon to completely scrap what you have.

In addition to jv's questions, here is a story from one of our skippers:

http://www.c34.org/wiki/index.php?title=Rebuilding_the_M25-XP

You may also find a lot of information about M25 series engines in our C34 Tech wiki: http://www.c34.org/wiki/index.php?title=Diesel_Engine

Before you depend on this mechanic, it seems most of us are suggesting that either you get another opinion or learn some more yourself so you can feel more comfortable with the input you're getting from any mechanic.

Like many, I'm not born a diesel expert, and don't consider myself one even now after owning one for 13 years, but I sure can do troubleshooting and most basic repairs and maintenance.

I would think you'd want to learn more before you make this big a decision.

If you answer the questions jv asked, I'm sure the skippers here will be more than glad to help you out.

Good luck.

Stu Jackson · Aug 2, 2011

and try to fire the engine while it is in gear and under a load.

Uh, please don't. That won't help your transmission any, and if the engine is gonna fire and he thinks the rings are stuck, starting in gear will make NO difference.

My gut reaction is that pouring anything BUT oil in a cylinder is just a bad thing.

Try for another opinion.

Heck, try calling the guy that was mentioned in the link I gave you earlier.

jviss · Aug 2, 2011

Clarification?

the po he said it went out on him last September 2010?

Can you ask him how or why it "went out?" Did it just quit? Overheat? Make bad noises? Lose power? Any smoke, smells?

By the way, sitting since Sept. 2010 won't cause all the rings to stick, causing compression. Mine sits from November to June or so every year, and starts on the first try.

jrowan · Aug 3, 2011

Also remember that Universal engines are totally different from others such as Yanmars which rely on good compression or they won't start. Universals rely on Glow Plugs to build up heat in the cylinder to aid in starting, and U should also check or just replace any worn glow plugs, as their cheap to replace. I doubt the pistons are seized, as U wouldn't be able to turn over the engine to even perform a compression test. As noted above, I would also confirm that the decompression valve is seated properly.

I would definitely get a second opnion from an experienced Universal diesel mechanic before I rebuilt that engine. Sometimes mechanics are just fishing for work. He should have performed the compression test FIRST, before replacing any injectors or parts. Even if the motor has a bad head gasket or piston rings, a rebuild is a lot cheaper then repowering, which is unecessary unless the block was cracked - & extremely unlikely. Good luck.

jimmcgee · Aug 4, 2011

Hopefully these links will help:

Best of luck,
Jim

jviss · Aug 4, 2011

M25 or M25XP?

I'm actually surprised the OP says it's an 'XP model engine. My 1984 C36 has an M25 - the difference being, the M25 is based on the Kubota D850, the M25XP on the D950. Can you check?

Thanks,

jv

Stu Jackson · Aug 4, 2011

jv, you're right, thanks for noticing. With a 1984 boat, unless the boat was repowered over the years (likely? or not?) it should be an M25 engine. Our 1986 boat has one. As I recall, the M25XP started going into late 1987 and certainly 1988 boats (C34s for sure, I know that for a fact).

As you noted, they are different Kubota blocks, but are essentially the same engine except for three major things: 1) increased HP from 21 to 23; 2) larger 3 inch HX; 3) "fixed" the old alternator bracket from cast to real steel.

I saw a good block comparison chart recently, here: Reply #7, ignore the rants in the first post (!): http://www.ericsonyachts.org/infoex...241-Universal-5432-amp-M40-engine-information

jrowan · Aug 5, 2011

ps. If the engine does manage to eventually start, runs, & the Hurth transmission works then U probably just need a tune up, etc. If U already replaced the injectors then that should help the diesel run smoother. If its sat for a long time, then I would pump out the old diesel fuel from the tank, change the fuel & oil filters, do an oil & trans. fluid change, etc.

By the way, the heat exchanger may not even need replacement, just cleaned out, unless its rusted through. I've seen sailors take them out, clean or boil out the built up corrosion, & then reinstall them for years of continued use.

Stu Jackson · Aug 9, 2011

Great to hear, thanks for reporting back.

Next word of caution: don't get too exuberant, yet, but also don't have 'em pull anything apart until you go step-by-step. Like, f'rinstance, sometimes they don't start 'cuz of bad engine ground connections and/or simple $1.83 fuseholders on the wire from the start button to the starter solenoid.

You might be interested in this: our C34 Critical Upgrades: http://c34.org/bbs/index.php/topic,5078.0.html

Check out the tech wiki under engines, too.